Frequently Asked Questions

About Anchor Bolts

Can I substitute a rod with a nut for a headed anchor bolt?

We strongly recommend against making any configuration substitutions without approval of the Engineer of Record. The term “headed anchor bolt” is somewhat ambiguous, but our interpretation of this product would be a bolt with a forged head, as opposed to a rod with a welded nut. If a galvanized, headed anchor bolt has been specified, there is a good reason the engineer chose that particular design. Making the decision to change configurations, or letting a bolt salesperson convince you that a rod with a nut is the same as a headed anchor bolt, could expose you and your company to a tremendous amount of liability.

What is the pullout strength of an anchor bolt?

We can provide you with the minimum strength requirements for a particular ASTM grade of anchor bolt, but you will need to consult with a structural engineer to determine the pull out strength of a specific size, grade, and type of anchor bolt. There are simply too many factors that affect the strength of an anchor bolt, including embedment depth, anchor bolt design, strength of the concrete, type of structure it is supporting, etc.

High Strength Anchor Bolts

What grades of anchor bolts can be galvanized?

All anchor bolt grades except A354 Grade BD can be hot-dip galvanized. There are two issues that come into play when galvanizing high strength anchor bolts that have undergone a heat treating process. The first concern is that the mechanical properties (strength) of the quenched and tempered anchor bolts could potentially be altered by submerging them in a tank of 840 degree molten zinc. Since the temperature of the zinc does not come with 100 degrees of the tempering temperature of the heat-treating process, and bolts are only in the tank for 2 – 4 minutes, theoretically the strength of the bolts will not be affected.

The second issue is hydrogen embrittlement, which can lead to premature failure of the anchor bolts when hydrogen is introduced during the galvanizing process. Only very high strength steels are susceptible to this phenomenon, and for this reason ASTM recommends against galvanizing A354 Grade BD anchor bolts. All other grades of anchor bolts can be hot-dip galvanized with no concern of altering the mechanical properties or subjecting them to the potential for hydrogen embrittlement. For a more in depth discussion of this issue, visit this FAQ on Portland Bolt’s main website.

What grades of anchor bolts can I weld to?

Technically, the only two grades of anchor bolts that can be welded are ASTM F1554 Grade 36 and F1554 Grade 55, but only when Grade 55 meets the supplemental requirement (S1) for weldability. All other anchor bolt specifications are manufactured from either medium carbon or medium carbon/alloy steels that develop their strength through a heat-treating process. When high heat is introduced (as in welding) to an anchor bolt that has been quenched and tempered, the strength of the anchor bolt may be altered.

Anchor Bolt Specifications and Substitution

Does stock all thread rod meet ASTM F1554 Grade 36?

Typically, commercially available mild steel all thread rod will not meet the requirements of F1554 grade 36. Most all thread rod that is readily available in the marketplace will typically meet the requirements of ASTM A307 Grade A. The difference between these two specifications is that F1554 Grade 36 anchor bolts have a minimum requirement for reduction of area (a value associated with the steel’s ductility), whereas A307 does not. Therefore, the test reports that accompany A307 all thread rod will not contain a reduction of area value and therefore cannot be certified to meet F1554 grade 36.

Portland Bolt stocks domestically manufactured mild steel all thread rod conforming to F1554 Grade 36, both black and galvanized, that has undergone reduction of area testing, and these values are reported on the accompanying test reports.

Will stock A307 Grade A hex bolts meet the requirements of F1554 Grade 36?

Imported A307 hex bolts will not meet the requirements of F1554 Grade 36 for the same reason that all thread rod typically doesn’t meet F1554 Grade 36; The test reports are missing reduction of area values. Additionally, imported mild steel hex bolts typically do not have a reported yield strength value, which is a requirement of F1554 Grade 36, but not A307 Grade A.

Portland Bolt stocks a line of galvanized F1554 Grade 36 hex head anchor bolts from 3/4” diameter through 1” diameter in lengths to 36”. We also stock headed blanks in other diameters that can be cut to length, threaded, and galvanized quickly to meet your delivery schedule.

Can A193 Grade B7 be substituted for F1554 grade 55?

No. All F1554 anchor bolt grades have a maximum strength requirement. A193 grade B7, which is readily available as all thread rod, possesses a minimum tensile strength requirement that exceeds the maximum tensile strength of F1554 grade 55. Therefore, this is not an acceptable substitution. When it comes to galvanized anchor bolts, stronger is not always better, and one should not assume that a bolt that exceeds the strength requirement of the specified product can be substituted without the engineer’s approval.

Galvanized Nuts

Are the threads of a galvanized anchor bolt cut undersize?

No. A galvanized anchor bolt will have a coating of zinc on the threads that typically varies from 2 – 6 mils (thousandths of an inch). Therefore, black (plain finish) and zinc plated nuts will not thread onto a galvanized bolt. Instead of cutting the threads undersize so nuts will fit, hot-dip galvanized nuts are tapped oversize to accommodate the zinc on the threads of a galvanized anchor bolt. ASTM A563 specifies the amount a nut should be tapped oversize when being used with a galvanized bolt.